. Hybridomas that secreted antibodies for aflatoxin B1 were selected using two immunization protocols referred to as A and B. Protocol A is a standard immunization method and resulted in the selection of only two clones that produced monoclonal antibodies against aflatoxin B1. In protocol B a unique immunization schedule which resulted in the generation of 10 hybridomas is described. Of the 10, one antibody was highly specific to B1, four antibodies reacted equally strongly with B1, G1 and weakly with B2. Another four reacted strongly with B1 and weakly with B2 and G1. One clone reacted equally strongly with B1, G1 and B2. Interestingly all the 10 antibodies showed little or no cross-reaction with G2.

Wheat and barley crops were shown to be susceptible to Indian peanut clump virus (IPCV) under field conditions. In wheat, the Hyderabad isolate of IPCV (IPCV-H) induced symptoms resembling the rosette caused by soil-borne wheat mosaic virus, and these were apparent only three weeks after emergence. Early-infected plants were severely stunted and dark green, with chlorotic streaks on the youngest leaves, which turned necrotic as the plants aged; most of these plants died. Late-infected plants were also stunted and were conspicuous in the field because of their dark green appearance as a result of delayed maturity. The virus was detected by ELISA and nucleic acid hybridization in all plants with symptoms. These plants usually produced fewer tillers than healthy ones. Spikes were malformed, often did not emerge from the flag leaf, and they contained few, shrivelled seeds. Grain yield was decreased, on average, by 58%. In barley, IPCV-H caused severe stunting and general leaf chlorosis. As the plants aged, the leaves became necrotic and the few infected plants that reached maturity produced small spikes. IPCV-H antigens were detected by ELISA in every wheat seed from infected plants and the virus was transmitted through wheat seed at a frequency of 0·5-1·3%. Storage at 4ЊC for more than a year did not affect seed transmission frequency. The virus was detected in leaves and roots of seed-transmitted plants. Seed transmission was not detected in barley. The Durgapura isolate (IPCV-D) was detected in wheat crops (cv. RR-21) at 3 different locations in Rajasthan State, India. Infected plants showed reduced growth without any overt symptoms.

Delfosse, P., Reddy, A. S., Legrève, A., Thirumala Devi, K., Abdurahman, M. D., Maraite, H., and Reddy, D. V. R. 2000. Serological methods for detection of Polymyxa graminis, an obligate root parasite and vector of plant viruses. Phytopathology 90:537-545.A purification procedure was developed to separate Polymyxa graminis resting spores from sorghum root materials. The spores were used as immunogen to produce a polyclonal antiserum. In a direct antigen coating enzyme-linked immunosorbent assay (DAC ELISA), the antiserum could detect one sporosorus per well of the ELISA plate. In spiked root samples, the procedure detected one sporosorus per mg of dried sorghum roots. The majority of isolates of P. graminis from Europe, North America, and India reacted strongly with the antiserum. Interestingly, P. graminis isolates from the state of Rajasthan (northern India), from Pakistan, and an isolate from Senegal (West Africa) reacted weakly with the antiserum. The cross-reactivity of the serum with P. betae isolates from Belgium and Turkey was about 40% of that observed for the homologous isolate. There was no reaction with common fungi infecting roots or with the obligate parasite Olpidium brassicae. However, two isolates of Spongospora subterranea gave an absorbance similar to that observed with the homologous antigen. The DAC ELISA procedure was successfully used to detect various stages in the life cycle of P. graminis and to detect infection that occurred under natural and controlled environments. A simple procedure to conjugate antibodies to fluorescein 5-isothiocyanate (FITC) is described. Resting spores could be detected in root sections by using FITC-labeled antibodies. The potential for application of the two serological techniques for studying the epidemiology of peanut clump disease and for the characterization of Polymyxa isolates from various geographical origins is discussed.Polymyxa spp. are soilborne, obligate intracellular parasites of roots, classified under the order Plasmodiophorales. Currently, two species, P. graminis Ledingham and P. betae Keskin, are recognized. They transmit at least 12 different plant viruses in the genera Benyvirus, Bymovirus, Furovirus, and Pecluvirus (1,30,32). Peanut clump virus (PCV) and Indian peanut clump virus (IPCV) are members of the genus Pecluvirus (40) that affect the production of peanut and monocotyledonous crops in West Africa and in the Indian subcontinent (3,9,40,43). In the absence of cost-effective methods for the management of peanut clump disease (40), it was essential to study its epidemiology with emphasis on identification of the hosts for the virus and P. graminis and their influence on the perpetuation and spread of clump disease. Epidemiological studies on an obligate parasite such as Polymyxa spp. are comparatively difficult and time consuming, because its detection has traditionally relied on light microscopic inspection of roots. However, results from these studies are expected to aid in the formulation of costeffective cultural practices ...

The progress of Indian peanut clump virus (Hyderabad isolate; IPCV-H) and its vector Polymyxa graminis in various monocotyledonous crops and groundnut was studied during the 1994, 1995 and 1996 rainy seasons in a naturally infested field in India. The roles of rainfall and temperature in the dynamics of infection by both the virus and its vector were analysed by exposing young seedlings for short periods in the field. Of the host crops studied, wheat, followed by barley, showed the highest virus incidence, although P. graminis was rarely observed in roots of wheat and was not detected in those of barley. The roots of maize, pearl millet and sorghum plants infected by P. graminis showed intense colonization by sporosori. IPCV accumulated in systemically infected maize plants; the sorghum and pearl millet cultivars studied showed a transient presence of IPCV-H. Rice was seldom infected by the virus and P. graminis was not detected in its roots. Groundnut was a systemic host for the virus, although during these experiments no P. graminis was found in its roots. Groundnut appeared to be susceptible to infection, mostly in the early stages of crop development, and the rate of IPCV-H transmission in groundnut seeds was highest (13%) for plants infected when young. The seedtransmission rate quickly decreased in plants showing symptoms 1 month after sowing. Time of infection had little influence on groundnut pod yield, which was always reduced by >60% in infected plants. There was some evidence that the quantity and distribution of rainfall influenced the incidences of IPCV-H and P. graminis : high rainfall resulted in high incidences of the virus and P. graminis , and a weekly rainfall of 14 mm was sufficient for P. graminis to initiate infection. Temperatures prevailing during the rainy season ranged from 23 to 30 ° C and were found to be conducive to natural virus transmission. These results suggest measures to be explored for controlling peanut clump disease.